When it is necessary to perform surgery on a patient's heart, the surgery has heretofore usually been accomplished by a major open heart surgical procedure, requiring general anesthesia and full cardiopulmonary bypass, with complete cessation of cardiopulmonary activity. Such surgery usually includes about three weeks of hospitalization and months of recuperation time for the patient. The average mortality rate with this type of procedure is about five to six percent, and the complication rate is substantially higher. Descriptions of open heart procedures can be found in Gibbon's Surgery of the Chest, 5th Ed., David C. Sabiston, Jr., M.D., Frank D. Spencer, M.D., 1990, Vol. II, Ch. 52, pp. 1566-1596, and Textbook of Interventional Cardiology, Eric J. Topol, 1990, Chs. 43-44, pp. 831-867.
In those cardiac procedures requiring cardiopulmonary bypass, a large clamp is applied to the exterior of the ascending aorta to close it off once cardiopulmonary bypass is established. However, application of such an external clamp to a calcified aorta may release emboli into the bloodstream. Further, upon the removal of the aortic clamp at the end of the procedure, any debris or thrombus generated during the procedure upstream of the clamp or by the clamp itself can travel into the brachiocephalic, the carotid, or the subclavian arteries, with serious results such as strokes and the like. For example, in up to 6% of the open-chest coronary bypass surgeries performed in the United States, there is noticeable degradation of the patient's mental faculties following such surgeries. This degradation is commonly attributed to cerebral arterial blockage from debris and emboli generated during the surgical procedure.
An endovascular system and procedure for performing cardiac surgery has been described in copending applications Ser. Nos. 07/730,559, filed on Jul. 16, 1991, 07/991,188, filed on Dec. 15, 1992, and 08/123,411, filed Sep. 17, 1993, the disclosures of which are hereby incorporated herein by reference. In these patent applications, an endovascular clamp is described which isolates the patient's heart from the patient's arterial system without the need for a thoracotomy. The endovascular clamp is an elongated intra-aortic catheter which is introduced into the patient's femoral artery and which has an occlusive balloon on a distal portion of the catheter. In the procedure described, the catheter is advanced through the patient's femoral artery and aorta until the occlusive balloon on the distal portion of the catheter is disposed within the patient's ascending aorta at a location between the coronary artery ostia and the brachiocephalic artery. The occlusive balloon is inflated or otherwise expanded in this region to occlude the aortic passageway and is maintained in the expanded condition until the completion of the procedure. The patient is placed on cardiopulmonary bypass to maintain circulation of oxygenated blood. Cardioplegic material is then introduced into the myocardium of the patient's heart either antegradely through one or both of the coronary arteries or retrogradely through the patient's coronary sinus or both. Following completion of the procedure, the region upstream from the occlusion balloon including the ascending aorta and the patient's left ventricle may be bathed in irrigation fluid, e.g. saline solution, and the fluid and any debris or emboli in the region can be aspirated through an inner lumen of the catheter to the proximal end thereof which extends out of the patient. When the aortic region and the left ventricle are free of debris, the balloon is deflated or otherwise contracted and the catheter removed so that normal blood flow can resume.
In the short period during and after the occlusion balloon is inflated, but before the cardioplegic material paralyzes the patient's heart, significant pressure pulses from the beating heart and the cardiopulmonary bypass system are applied to both ends of the inflated occlusion balloon. This may displace the occlusion balloon from its desired position within the ascending aorta, causing damage to the aortic valve, or occluding the ostia of the coronary arteries, brachiolcephalic anew or other artery.
What has been needed and heretofore unavailable is a means to securely position the occlusion balloon within the ascending aorta so that the pressure pulses received on the ends of the occlusion balloon do not displace the balloon from its desired position. The present invention solves this and other problems.
The descriptive terms "downstream" and "upstream", when used herein in relation to the patient's vasculature, relate to the direction of normal blood flow and to the direction opposite normal blood flow through a vessel respectively, i.e., "upstream" is closer to the heart in the arterial system and further from the heart in the venous system. The terms "proximal" and "distal", when used herein in relation to instruments used in a cardiac procedure, refer to directions closer and farther away respectively from that end of the instrument which is held or manipulated by the operator performing the procedure.